The referenced U.S. Pat. No. 4,856,494, SCHUSSLER et al, the disclosure of which is hereby incorporated by reference, describes a solar heating system and the various positions which the mirror system has to assume as the earth and the sun move relative to each other. Various types of solar systems are coupled to automatic positioning apparatus which move the mirror system in accordance with the position of the sun. The mirror system must move, to follow the sun, about an angle of approximately 180.degree.. At night, the mirror system is additionally deflected so that the mirror will face downwardly, so that its reflective surface will not be impaired by deposits, dust, dirt, or precipitation of any kind, for example rain or snow. Thus, the mirror must move not only about the 180.degree. determined by relative movement of the sun but, additionally, tip downwardly beyond a predetermined dead point so that, within any 24 hour period, the mirror may have to move about an angular range of between 200.degree. and 270.degree.. This angle is covered by the movement of the mirror, or the mirror system, twice during any 24 hour period, once to move the mirror from the "night" position to follow the sun, and then, after the sun has set, back towards the "night" position.
The connection to a heat exchange arrangement must, likewise, move with the mirror, and hence move twice every 24 hours over the mirror angular range. Heat exchange systems typically include a heat exchange fluid, which heats as solar radiation is concentrated thereon. Relative movement, thus, will result between the heat exchange arrangement on the solar heater itself and a fixed heat exchange fluid connection or coupling point. To compensate for the movement, it has been proposed to connect the fixed coupling or connection point and the heat exchange arrangement with a flexible hose, typically a corrugated flexible hose. Such flexible hoses are subject of extreme requirements. They are under high pressure, for example a pressure of over about 40 bar, retaining fluids, typically liquids, which will reach a temperature of between 300.degree. to 400.degree. C.
Difficulties with such connections and such hoses have been experienced and the referenced U.S. Pat. No. 4,875,716, WINZEN et al, describes a solution. The flexible hose, as the mirror system moves, changes its direction of bending. The direction of bending changes rapidly, in what might be termed a "snap-over" manner. The position at which the bend snaps over from one direction to the other is indeterminate and changes with the direction of movement of the mirror, for example it snaps at different positions when the mirror follows the sun and when the mirror returns after sunset to the initial and then the "night" position. This snap-over substantially stresses the flexible hose and resulted in failures of solar heating systems. The referenced patent describes arrangements to decrease the stresses on the hose and to increase the resistance to failure.
The system described in the referenced U.S. Pat. No. 4,875,716 provided a substantial improvement over prior art systems. Yet, the hose proved to be difficult to make and was expensive. cl The Invention
It is an object to further improve a solar heating system of the general type described in the referenced U.S. Pat. No. 4,856,494, in which the loading on the hose, and particularly the bending stresses are reduced, so that the system is further improved and the lifetime of the replaceable bending hose is still increased.
Briefly, a hose which is shorter than that previously used is coupled to a fixed connecting point for heat exchange fluid through a movable coupler which can move radially with respect to the axis of rotation of the mirror system, for example along a radial line connecting the mirror pivot axis with the fixed heat exchange arrangement on the mirror system, and which rotates with the mirror system. The coupler is located, preferably, at the circumference of a theoretical circle which has a center at the mirror pivot axis and at a radius corresponding to the distance between the mirror axis and the heat exchange arrangement. The coupler can be connected to the fixed heat exchange fluid connector by a rigid pipe which, in turn, is coupled to the heat exchange connector by a movable joint, the movable pipe pivoting about the flexible connector and permitting movement of the coupler between the pipe and the flexible hose along essentially the radial line passing through the mirror pivot axis.
The invention is based on the discovery that the solution to the problem of connecting the heat exchange arrangement, which moves with the mirror to a fixed supply-and-drain connection, cannot be obtained by improvements in the flexible hose as such but, rather, requires an entire rethinking of the operation of the solar heating system. The pressure and temperature loading placed on the flexible hose cannot be changed; the pressure and temperature parameters are given by the design of the solar heating system. A decrease in stresses placed on the flexible hose can be obtained only by revision of the kinematic relationships affecting the hose as it changes its position upon movement of the mirror system. Analysis, based on this discovery, has shown that in the end region the pivot radii of the hose are small, and thus place heavy bending stresses on the hose, which is particularly detrimental to the hose since the stresses change in direction as the mirror first, for example, moves towards the "night" position and then reverses direction as the sun rises. The analysis has further shown that at the "noon" position of the mirror system, the flexible hose is in essentially stretched position. This stretched position defines a certain length between the heat exchange arrangement and the fixed fluid connections. This length of the stretched hose must be fitted to a smaller distance when the mirror is in the terminal positions, e.g. "night" and "sunset". A substantial length of hose was thought necessary to prevent tight bending radii.
In accordance with the present invention, however, the hose has been shortened substantially and, rather, the coupling of the hose to the fixed heat exchange fluid connection is made movable, so that the coupling can move as the mirror system rotates. This permits much better placement of the hose in the region of the mirror system and much more favorable bending radii for the hose. As the mirror system moves from a noon position, in which the hose is stretched, towards the terminal positions, the coupling also moves away from the center of the pivot axis so that in the end regions of the pivot angle of the mirror system, the hose is bent only along a simple, essentially part-circular curve which can be readily accomodated by hose of standard construction.
In accordance with a particularly advantageous feature of the present invention, the hose can be made substantially shorter than heretofore, for example less than half the length previously thought necessary, since snap-over regions of the hose are no longer needed. This renders the connecting hose not only substantially less expensive, but also permits a more compact construction of the entire heat exchange fluid system.
In accordance with a preferred feature of the invention the coupling of the hose is connected to an elongated rigid pipe which is connected by a flexible coupling to the fixed connection for the heat exchange fluid, the essentially rigid pipe permitting movement of the coupling to the hose along a shallow arc having at its terminal points the positions of the coupling for the hose when the mirror is in the "noon" position and when it is in "night" position.
The length of this pivot arm formed by the rigid pipe, and the flexing angle of the pivot arm, or the pivot angle, defines the positioning path of the coupling element, extending essentially radially to the pivot axis of the mirror system. The flexible hose can be connected to the end of the pivot pipe via a flexible coupling in order to prevent formation of a sharp bend of the hose adjacent the coupling. Likewise, the hose is preferably connected to the heat exchange arrangement, exposed to the solar radiation, by a flexible coupling.
If the overall system is of substantial size, so that the flexible hose itself will be of substantial length, one or both of the flexible connections between the coupling and the hose may be omitted, since the flexing capability of the hose itself may be sufficient.
The connection of the pivoting pipe with the fixed heat exchange fluid connection can be done by a flexible connector or an angle compensating system of well known construction. Preferably, and particularly in view of the requirement of absolute tightness, a closed, sealed construction, in which substantial pressures can be retained, arrangements which are similar to a corrugated or bellows type construction are preferred.
In dependence on loading, degree of the pivot angle and overall layouts, one or more angle compensator or bellows connector can be combined. To prevent possible failures, the deflection of any one of the connectors can be limited, for example by limit stops, so that the bending angles of the respective angular connectors are restricted, each, to safe and acceptable levels.
In accordance with a preferred feature of the invention the movement of the pivoting pipe likewise is limited by a stop. This permits control of the position of the flexible hose to set the bending angle through which the flexible hose must bend to a desired curve portion. In an ideal situation, the curve is essentially part-circular.
The pivot pipe can move as required by mirror rotation. It will return to its final position usually by gravity. If frictional losses or other couplings apply forces insufficient to permit return of the pivot pipe to a predetermined end position, additional loading by weights or springs may be provided.
The flexible hose, itself, can be of any suitable construction, well known in such systems. In accordance with a preferred feature of the invention, however, the flexible hose preferably has an oval or elliptical cross section, in which the larger cross-sectional axis extends transversely to the bending axis of the flexible hose. Alternatively, a plurality of hose elements of circular cross section can be located next to each other, for example surrounded by a common sleeve which may include insulation material, the respective individual hose elements being located next to each other transversely to the bending axis of the overall hose system.
Unitary systems can be used, as well as hose systems having three or more parallel hose elements or hose units which, for example adjacent the connection to the heat exchange arrangement, are joined or commonly coupled thereto; a similar joining or common connection is provided adjacent the radially movable coupling. Such multiple unit-single unit connectors are well known in the fluid handling industry, and any suitable arrangement may be used.